Electrical condenser and method of making it



lll. 519,868 tiled December 5, 1921, which has nowY eventuated intolatent 1,499,103, dated July 1, 1921, which patent 1s a continuation inpart of lil. L165,13?, iii-ed April 26, 1921,

rl`his application is a division o1 which has now eventiiated intoPatent 1,558,043, dated October 20, 1925. also this appli ation is a.continuation in part ot S. lil. 456,903 liled March 30, 1921, which hasnow eventuated into l)atent 1,652,212, dated De ceinber 13, 1927 andwhich in turn is a continuation in part of S. N. 332,421, tiled @ctober22, 1919, which has eventuated into Patent 1,695,060 dated Beceinber 11,19.28.

'lf he type ot condenser embodying the present invention is known as amica condenser inasmuch as it usually comprises a stach composed otalternate sheets ot toil and dielectric, the toil consisting preferablyof a soft material such as lead or tin, and the vdielectric consistingpreferably et mica, which is one ot the best dielectrics known tor thispurpose.

rl`he stacks each are made up of sections connected in series withseparators between the sections, and are clamped and secured within asuitable casing, the casing prefeifa bly in service constituting one ofthe terniinals ot the condenser, or an electrical connection betweenstacks.

Fig. 1 shows a longitudinal section ot one embodiment of thisinvention.`

Fig. 2 shows a detail of the stack construc-L tion.

Fig. 3 is a top plan View ot the construction shown in Fig. 2.

ln Figs. 2 and 8 of the accompanying drawings, l have illustrated aforni ot stack which 1 prefer tor use in the form ot the condenserillustrated in Fig. 1, although the stack ot Figs. 2 and 3 is ofgenera-l application. rlthe showing in Fig. 2 is an expanded View; thatis, the several parts ot the stack are shown with intervening spaces tomore readily illustrate the construction of the stack andthe inethod ofbuilding' the same. When assembled in the condenser, the several sheetsare in mechanical tace Contact, being t i ou ion suitably clampedtogether to to in so (eith Vith or without i material ad .ling ""lthereto as cori-ling to coi/iditions), the clamping means being snch asdisclosed in Fig. 1, the stacks illustrated therein beingconsideredstacks ot the type shown in Figs. 2 and improved stack comprises one ori separators 5'5", each et which conc` several layers of inica,perrnissively and de sirably, cheap or detective mica, or they may'consist ot sheet niieanite or other insulatin J1' material. :Folded orwrapped overl opposite faces of each separator, 5"?, is a foil sheet 58forming conduction sheets (aiifnatures} on opposite taces ot tj rJ'he neseparator 57. folded halves ot the toil 58 uson opposite faces otseparator 5'? are spaced inwardly :troni three edges thereof formingmargins 60, as shown in Figs. 2 and 3. r1he'sheets 58 may be Very easilyfolded around the separators with their ends in line, thus properlycentering the toil on each separa-tor. The two (physically parallel)folded or wrapped halves ot given foil sheet 58 are, in the eaarnpleshown, electrically speaking, parts ot two separate stack-sections, eachot which sections electrically complete in itselii, and two -of whichsections lie adjacent to one another in the stack, said sections beingsenarated troni one another at their opp os'- e a 0 "t, Jlaces by aseparator 57. For each stachsection consists, in the simple illustrativeexample shown, of a single goed (not detecn tive) thin inica sheet 61,and on the respective tacos thereof', two halves of successive foldedtoil sheets 58. rlwo successive sections, so constituted, are separatedfrom one another by a section-separator 57.7, such successive sectionsbeing electrically connected together in series with one another byineans of the integral bend or fold 59 ot the folded toil sheet 58. rtheterminals of the entire stack are at the ends ot the stack ot separatesections (see 22, 23 in Fig. l), since the successive and adjacent, butelectrically separate sections, successively spaced from one another attheir faces by section-separators 57, are electrically connected inseries with one another troni end to end ot the stack by means of saidintegral bends or folds 59 of the successive wrapped or foldedfoil-sheets 58;

-although every two successive foil-sheets 58 are separated from oneanother by the thin mica sheets 61 which constitute the dielectrics ofthe several stack-sections, Heretofore, the practice in suchseries-sectional condenser stacks has been to employ separate,individual foils for each stack-section, each foil lying (unfolded) in asingle plane, and the ends o-f the foils projecting individually out ofthe sides of the stack sections; and to obtain the series-connection ofsections in the stack, the practice has been to fuse (solder) togethersuch projecting ends of foils from two successive sections, such sets offoils projecting from the same side of the stack. In this invention, asabove, the series connection is in a bend or fold 59. In a design ofstack havingseries-connected sections to withstand high potentials butwherein the desired capacitance is low (and, therefore, not many foilsfor each section), this invention obviates the necessity of the abovesoldering operation, in addition to reducing the labor-charge in foilpick-up, i. e., only one lact of the operative in picking up a foil 58is needed in lieu of picking up two foils separately and successively asheretofore.

As shown'in Figs. 2 and 3, each folded foil-sheet 58 has sufficientlength to overlie substantial portions of the adjacent faces of a.section-separator 57 and the two mica sheets 61 above and below aseparator 57; but the total length of each foil-sheet 58 is suiicientlyless than twice the width of section-separator 57 and mica 6l as toleave a foil-free margin along the edges thereof, over which thefoil-sheet 58 does not extend; and particularly this results in forminga foilfree margin alongv that edge of dielectric 61 which is opposite toits edge adjacent which foil-sheet 58 is wrapped. It is the aboveelectrically independent sections which are connected in series with oneanother bv the integral bendy yor fold 59 of the wrapped foil-sheet 58.Onehalf (or a little less than half) of the complete separate foilsheet58 overlies the good mica sheet 61, which,` in the example illustrated,constitutes the dielectric of a stack-section. But the two halves of agiven separate foil-sheet 58 overlie the opposite faces of separator 57.As shown in Fig. 2, separator 57 may consist of two or more thin sheets,preferably of mica, and permissively and economically (a-ltho notnecesssarily) of defective mica otherwise wasted. The effective stackarea in the eX- ample shown in Figs. 2 and 3 is that area by which thewrapped halves of foils 58 as armatures overlie the good'mica-dielectricsheets 61, all of which latter exactly overlie one another in the stack,as shown in Fig. 2.

The method of building a stack embodying the invention (with or withoutthe waxing ije- 57, with the bend of thefoil, say, at the left,

as shown. A good mica sheet 61 is laid on top of that. (These singleseparate good mica sheets 61 may be of the same area as the separators57, as shown.) Then a second foil-wrapped insulating sheet 57 is laid ontop of the top of the said last mica sheet 61, but the foil-fold 59 ofthis second combined element 57-58 is located on the opposite side(right-hand, as shown) of the condenser stackfrom the foil-fold (at' theleft) of the'like combined element below it. Thus is formed one completestack-section consisting of a good separate 'mica sheet 61 (the secondone from the bottom) and of two separate halves of two successive foldedfoilsheets 58, said separate halves lying on opposite faces of said micasheet 61 and insulated from one another by said sheet. Next, anothermica sheet 61 is laid on the top of the growing stack. Then a thirdfoil-wrapped insulated separating sheet 57 is laid on top of that, withits foil-wrapped edge at the left. 'This completes a secondstack-section consisting of a .good mica dielectric and of foil-sheets.on the opposite faces thereof which are separated from one another bythe interposed mica sheet 61 itself, constituting the dielectric of thesecond stacksection. This process may be continued as illustrated inFig. 2 to produce a stack with additional sections to withstand higherpotentials; or the invention may be embodied in other forms of stacks. j

Thus each section of a series-sectional stack embodying the invention inthe form shown in Figs. 2 and 3 comprises a single good mica sheet 61and two electrically separate /foilsheets, one on each face of said micasheet; said two foil-sheets being halves of two separate completewrapped foil-sheets. 58; and each pair of adjacent sections of suchconstruction are electrically connected together in series by theintegral band or fold 59 ofa complete foil-sheet, which is wrappedaround an insulating sheet 57 between such two stacksections. l

The wrapping of a foil-sheet over one edge of separator 57 leaves theopposite edge free of foil, which free edge projects from the stack(Fig. 1) so as to lie between two successive integral connections 59 onthe same side of the stack, and serves to insulate and separate from oneanother each two successivheland adjacent stack-sections, each comprlsmga mica dielectric 61 and foils on opposite faces thereof. p Thisopposite projection of successive separators 57 is shown at 62 in Fig.3, and in Fig. 2 Where the second and fourth separators 57 from thebottom lie a little to the left of the first and third separators 57from the bottom, said second and fourth separators therefore projectingfrom the left of the stack; the right-hand edge of said second andfourth separators from the bottom lying a little to the left of therighthand edge of mica dielectric section-sheets 61, as Well as a littleto the left of the righthand edgeof the first and third separators 57from the bottom.

The separators A57 need not be of insulating material because the foilportions. on the opposite sides of each separator are connected togetherat 59; but When, as is shown in Figs. 2 and 3, the separators 57 havethe same optline or configuration as the dielectrics 61, it isadvantageous to constitute 57 of insulating material because then thereis no conductor extending from the foils to the edges of the stack to beliable to cause ash-over at such edges from an armature of one potentialat an adjacent armature of different potential. The increase in lengthof the stack by a thick separator 57 (Whether composed of one or severallayers of insulating material or conducting material) lis not onlyunobjectionable as compared With the economy resulting from the use ofthe invention, but it is alirmatively advantageous in the high potentialcondenser disclosed, in that the plurality of separators 57 so increasesthe `distance between the ends of the stack as to materially reduce theliability to flash-over through the usual insulating embedment W of Fig.1, such as Wax, and even more so through air.

The construction above described, or equivalent of it Within the scope0f the invention, is of distinct advantage in being easy to assemble atlow cost, and is of special advantage Where a stack of low capacity andrelatively high voltage is required, as in Fig. 1. The stacks of thepresent invention, as illustrated in Fig. 1, may be assembled, in part,by the process described in my copending application Serial No. 456,903,tiled March 30, 1921. The process therein described covers themanufacture of a stack by preliminary dipping the individual sheets ofmica in suitable insulating material, such as molten paraflin, andbuilding what is called the material `stack consisting of alternatesheets of foil and dielectric, the sections being assembled andconnected by any desired method, such as that illustrated in Figs. 1 and2, and then treating the material stack thus formed in molten insulatingmaterial, such as paraiiin, and applying high compression, and cooling,forming a solid block.

The construction above described or equivalent of it Within the scope ofthe invention is of distinct advantage in being easy to assemble at lowcost, and is of special advantage Where a stack of low capacity andrelatively high voltage is required as in Fig.` 1. The cost reductionincludes both metal and labor.

The highest saving is in mica, which is the item of highest cost in micacondensers; and

in the construction disclosed, the folding or Wrapping of the foilsaround section-separators 57 lpermits the greater proportion of mica inthe -entire stack to consist of defective mica sheets, if desired,thereby not only obviating the necessity of using good mica sheetsthruout the stack, but affecting a double saving in permitting the useof mica which otherwise would be entirely Wasted. The foils are cheapand the extra amount of foil here used at the folds orseries-connections 59 in Figs. 2 3 is immaterial.

As to labor cost, since the operative can fold the foils as readilyaround separators 57 as to build up a stack of, unfolded foil sheets (i.e., tWo separate foils instead of each folded foil 58) there is no extracost in such folding; and the labor saving is in the operatives pick-upof foils', which is reduced 50% by this invention.

The net saving in mic'as and labor is an important factor, which greatlyreduces the total cost of the condenser, the cost of the stack being theprincipal item in the cost of the complete condenser shown in Fig. 1.

The stacks of the present invention as illustrated in Figs. 2-3 may beassembled in a complete condenser as shown in Fig. 1, which, however,shovvs, for the purpose of comparison, the prior construction of stacks.That is, the stacks as shown in Figs. 2-3 are to be substituted for thestacks S, S1, of Fig. 1 and the compressing means and terminals thereof.In Fig. 1, the central metal stud 25 is the high potential terminal ofthe condenser, and the metal casing is the low potential terminal; stud25 being connected to the facing ends of the two stacks; the casing 10being connected to the other ends ofthe stacks; and allthestack-sections being separated from one another by the insulatingseparators (57 of Figs. 2-3) which project from the sides of the stacks,as do the prior art section-separators shown in Fig. 1. Of course, thestacks of Figs. 2-8 may be. assembled in a complete condenser in otherways, Fig. 1 being merely an illustration of an actual commercialassembly.

The stacks of this invention may be processed in part by the processdescribed in my copending application Serial No. 456,903, filed 30 March1921.

After the stacks SS', including the separators, have been waxed andcompressed, cooled and tested, they are in condition to be handled,being cold and covered with Wax,

After all the parts have been assembled.

' as illustrated in the drawings, with stacks SS held under sufficientpressure to hold them ,in place, the whole condenser can be invert-ed,the bottom 14 being removed, and

casing 10v filled with insulating material YV,

preferably molten parafiin or oil, in the manner described in myapplication 456,903 above mentioned, to provide a compact, non-porous,holosteric embedment W for they stacks and around the bushings andterminals within the casing 10, which is free from air and voids.

' As described in such application 456,903, a

head or extension is secured to the casing and the casing and extensionare preliminarily heated by filling the same with molten paraffin at atemperature around 146O C. While thus filled, the final pressure isapplied to stacks SS by tightening up screws 21. The molten paraflin isthen removed and vacuum applied and the casing and extension filled withmolten paraffin or other insulating filler, which is allowed to solidifyfrom the ybottom upwardly in the manner described in said application456,903. ln some cases, the preliminary heating with paraliin may beomit-` ted and the stacks SS linally clamped under high pressure as soonas positioned. The condenser stacks and terminals 25 are then embedded,and the head and surplus wax or insulating material removed as describedin said application 456,903. y,After the embedf ment, the bottoni 14-with its intervening gasket 15, is secured lin place by means of thescrews 16.

I claim 1. In an electrical condenser-stack of the type characterized bya plurality of sheets of dielectrics and metal foil armatures, the stackbeing separated by spacing sheets into a plurality of sections which areelectrically connected in series for high potential service1 theimprovement which consists of folded foil-sheets around-an edge of thesectionspacing sheets, whereby the foil-folds constitute theseries-connections between the successive stacl :-sections;the lengthsof the folded foil-sheets being approximately twice the width of thespacing sheets; a foil-free margin being left at the ends of such foldedfoil-sheets and at the edges of the spacing sheets opposite to thosearound which the 'Y foil-sheets are folded; the folds of succesrelate/isive folded foils being spaced peripherally of the stack with respect toone another.

2. An electrical sheet condenser-stack comprising dielectric sheets,metal foil sheets,

sheets separated into sections by spacing sheets for high potentialservice, the successive sections being electrically connected togetherby foil sheets as armatures, which are doubled around an edge of saidspacing sheets, the lengths of the folded foil sheet armatures beingapproximately twice 'the width of the spacing sheets.

4,' An electrical condenser-stack comprising a plurality of foil sheetsand dielectric sheets separated into sections by spacing sheets for highpotential service, each section respectively on opposite sides of aspacing sheet comprising, for low capacity service, a single pair offoil sheets and a single dielectric sheet between said pair of foilsheets, the two foil sheets on opposite sides of the spacing sheet beinghalves of asingle foil sheet which is folded over an edge of the spacingsheet, the length of the folded foilsheet being approximately twice thewidth of the spacing sheet.

A condenser comprising a plurality of sections composed of conductingelements and intervening sheets of mica of good dielectric propertiesand a separator of relatively thicker inferior grade mica between eachpair of sections and having adjacent conducting elements upon oppositefaces thereof integrally connected together around an edge of theseparator.

6. An electrical condenser stack, comprising a plurality ofsubstantially rectangular. sheets of dielectrics and metal foilarmatures separated into sections by substantially rectangular spacingsheets; the foil sheets in two adjacent sections so spaced being doubledby being folded over one edge of t-he intervening spacing sheet; thelengths of the folded foil sheets being approximately twice the width ofthe spacing sheets; and the folds of the foil sheets around successiveyspacing sheets being located at opposite sides of the stack.

7. A series-sectional high potential electrical condenser-stackcomprising sheets of dielectric and of metal,l foil armatures; spacingsheets separating the successive sections lvfrom one another; and thefoil armatures comprising sheets in length approximately one-half thelinear dimension of the spacing sheets and folded over an edge of thelatter, leaving ay margin at the opposite edge therelili of saidfoil-wrapped spacing sheets being disposed in the stack angularly withrespect to one another, whereby thev folds of successive foil armatureslie atdifferent sides of the stack, and the foil-free margins of thespacing sheets lie between two foil-folds at the same side of the stack.

8. An electrostatic condenser comprising a stack of sheets, saidstack-sheets comprising armature sheets and sheets of insulatingmaterial, said armature sheets comprising at least one pair of metalvfoils the individuals of which pair have their facing-together surfacesspaced from one another and their facing-away surfaces lyingrespectively adjacent to different dielectric sheets of the stackwhereby each individual of the pair acts sep'- arately as an armature,but said pair being constituted of a single foil sheet folded at itsmiddle and thereby constituting an electrical connection between theindividual separately acting armatures of the pair, said folded middleportion extending outside of the stack as a common terminal for the twoarmatures of the connected pair.

9. A high potential, low-capacity condenser comprising a plurality ofthin sections, each consisting of@`r thin dielectric sheet and two thinfoil armatures on the respective faces of such sheet; and spacing-sheetsbetween the successively adjacent stack-sections and increasing thethickness of the stack of thin sections for the application of higherpotentials across the condenser terminals without resulting lashover;said foil armatures respectively being folded around the edges of thespacing-sheets and their folded bends connecting successive thinsections together.

WILLIAM H. PRIESS.

